Identification badges have come into general use because of the need to discriminate between authorized persons and between employees and non-employees, as well as other groups. Improved security of a facility or a business is achieved when an effective identification badge system is empolyed. A recent survey of commercial card identification systems, whether photographic, visual, magnetic, electromagnetic, infrared, etc., illustrates the high security nature of many of these badge systems and their widespread application. However, the high security performance of each prior art badge system relies on the fact that each coded badge is assigned to one individual, and that the individual is uniquely linked to the badge itself by some physiological factor such as a photograph, finger print, hand geometry, signature, voice print, etc. When this physiological link is unavailable for use, the identification badge can be employed improperly, such as transferring the card from person to person, or admitting a person into excluded areas.
Where a physiological link is employed, the issuance of such a badge can be quite time consuming and suffer from other drawbacks, as well. Also, the determination of whether such a badge is valid or expired often requires close scrutiny, which is not always possible. Visitor badges and other temporary badges are a weak link in most security badge or card systems. This is because the individual is issued the badge for only a few hours or days, and the badge does not contain the physiological information of all other badges employed at the location. There is, in a temporary badge system normally no photograph of the visitor, nor his handprint. nor even his signature. Thus, a visitor badge may be used and re-used, improperly, by many different people and in most locations in a facility, including high security or confidential areas. This is because the temporary badge will be used by almost every type of person; salesman, serviceman, visiting scientist or engineer, advertising and marketing personel, accountants and auditing personel, etc.
As is widely known, temporary and visitor badges are frequently lost and/or forgotten to be returned. It is commonly experienced that frequent visitors may retain one of the visitor badges in order to bypass the time consuming check in procedures.
The present invention overcomes, or at least alleviates, these problems with prior art badges, by utilizing elapsed time indicating techniques, which rely on light exposure, an excellent method of indicating or measuring such time, provided the light intensity levels of the illuminated environments where the badge will be work, are relatively constant. This avoids transient and variable light effects on the badge which ean change the time characteristics of the badge. Because of the legal and operational requirements to provide adequate illumination in factory and other work facility, and good industrial engineering design for office buildings and businesses, a relatively constant illumination level generally does exist at facilities where temporary security badges will be employed. Thus, the elapsed time measuring means of the present invention, employed in the relatively constant illumination of this indoor environment is suitable for the physical stimulus required for these security badges. Alternately, outdoor illumination is also within reasonably close limits and an elapsed time indicating badge can be based at this illumination level.